Taxonomy and taphonomy of Pliocene bulimoid land snails from Māngere, northern New Zealand, with descriptions of a new genus and two new species (Gastropoda: Bothriembryontidae: Placostylinae)

ABSTRACT

Two species of bulimoid land snails, Maoristylus pliocenicus n. sp. and Archaeostylus n. gen. manukauensis n. sp., in family Bothriembryontidae, subfamily Placostylinae, are described here from fossil shells that were recovered from subsurface Kaawa Formation shelly sediments at Māngere, northern New Zealand. These fossils are of late Pliocene age (Waipipian Stage [latest Zanclean-early Piacenzian], 3.7–3.0 Ma), and are the oldest known representatives of the Placostylinae. The associated fossil fauna indicates that the land snail shells were deposited at shallow subtidal depths in a coastal inlet. The teleoconch of Maoristylus pliocenicus n. sp. has highly distinctive rugose sculpture and in this regard is very similar to modern M. etheridgei (Hedley, 1891) from Lord Howe Island. The latter taxon was described as a subspecies of M. bivaricosus (Gaskoin, 1855), but it is here treated as a separate species on account of its distinctive shell morphology. Archaeostylus n. gen. manukauensis n. sp. has apertural morphology that differs markedly from other taxa in Placostylinae. Rather than being ancestral to extant taxa it probably belonged to a sister lineage. Both it and the M. pliocenicus n. sp. lineage went extinct in New Zealand during latest Pliocene or Pleistocene time, possibly as a consequence of a cooling climate.

http://zoobank.org/urn:lsid:zoobank.org:pub:68553D05-C54C-4EFE-AF08-C7E4A17E5B0C

KEYWORDS:

• Maoristylus pliocenicus n. sp
• Archaeostylus n. gen. manukauensis n. sp
• Placostylus
• Kaawa Formation
• Waipipian Stage
• Lord Howe Island

Acknowledgements

The fossils described in this paper were found by Stefano Vittor (Ghella Abergeldie Joint Venture), Julianne McCoun (University of Auckland), and Nathan Collins and Thomas Stolberger (AIM). We thank Watercare Service Limited, especially Bernice Chiam, Shayne Cunis and Ron Boyle; Ghella Abergeldie Joint Venture, especially Alex Parma and Sandra Edwards; Waiau Pa Bulk Haulage and Mana Whenua Kaitiaki Forum, for allowing and facilitating access to the shelly sediments excavated during construction of shafts for the Central Interceptor, and for undertaking mechanical sieving of the sediments. Watercare Service Limited provided funding for AIM to employ Nathan Collins and Thomas Stolberger for five months from August 2021 to search the sediment pre- and post-sieving, and process and curate fossil material; Rebecca Bray and Nicky Pridham (AIM) ran this project and oversaw the funding respectively. We also thank Alan Beu and Dennis Gordon for identifying molluscs and bryozoans obtained from sediment inside the apertures of the fossil land snail shells; Wilma Blom (AIM) for arranging photography and curation of fossils, and suggesting improvements to the manuscript; David Sanderson and Jennifer Carol (AIM) for photographing specimens; Severine Hannam (AIM) for providing logistical support; Martyn Kennedy for advice on genetics and help with library searches; Kerry Walton for commenting on an early draft of the manuscript; and Chris Hollis and an anonymous referee for suggesting improvements to the submitted manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The authors confirm that the data supporting the findings of this study are available within the article and its Appendix.

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.